To change the hostname of your Ubuntu installation, edit the file hostname located under the /etc directory.
That is to say run the following:
You most likely would need to have administrative privileges to save changes to this file.
After making changes to this file, reboot the system and you should have the new hostname in place.
Some Linux distributions may not come with with the handy Users and Groups utility that allows you manage users and groups.
To install that, run the following command:
apt-get install gnome-system-tools
Some Ubuntu Linux distributions may not have come with the very handy Ubuntu Software Center.
In which case, you can install it by running the following command (assuming you have apt-get command):
apt-get install software-center
While exploring various Linux distributions, you may occasionally encounter a Linux distribution that does not come with the very handy Synaptics Package Manager. Assuming you have apt-get command, run the follow command:
apt-get install synaptic
This will install Synaptics Package Manager.